442 MANUAL OF HISTOLOGY. 



sue. All the different kinds of ducts show a lining composed 

 of a single layer of short cylindrical cells, containing ellipsoid 

 nuclei. The character of the lining cells is, however, gradually 

 changed as the acini are approached, near which it merges into 

 the alveolar epithelium by insensible gradations. 



Surrounding the nipple is a variously pigmented ring, called 

 the areola mamma. Its surface is slightly corrugated, and 

 this circumstance, taken in connection with its pigmentation, 

 results in the production of the marked contrast it presents to 

 the very white and soft integument covering the other portions 

 of the female mamma. The areola is also provided with abun- 

 dant unstriped muscle-fibres. Some of the latter surround the 

 nipple in concentric rings, others pursue a radial course. The 

 sudoriferous and sebaceous glands of the areola are conspic- 

 uously developed, and lanugo hairs are also found. The fa- 

 miliar changes which go on in the areola simultaneously with 

 the development of pregnancy, are mainly due to increased 

 blood-supply and additional pigmentation. The areola is also 

 provided with small granules of secreting parenchyma. Some 

 of these grains empty the products of their secretory activity 

 by special recurrent ducts into the main excretory canals. But 

 there are others which have special openings upon the free sur- 

 face of the areola. Usually, little papillary eminences mark 

 the presence of such orifices. These scattered bits of mam- 

 mary parenchyma are known as the glandules aberrantes of 

 Montgomery. Kolliker and others regard them as largely 

 developed sebaceous glands. 



The arteries of the mamma are chiefly derived from the 

 internal mammary artery and the long thoracic. The veins 

 empty into the thoracic branches and cephalic vein. Both 

 arterial and venous vessels proceed subcutaneously from the 

 periphery to the nipple, whence branches are given off in a 

 posterior direction. They are not guided in their course by 

 the distribution of the milk-ducts, but are distributed to the 

 glandular parenchyma in such a way that each lobule has its 

 own separate supply. Finally, under the areola the veins of 

 the nipple form a circular anastomosing chain, known as the 

 circulus venosus of Holler. Capillary vessels surround the 

 acini, forming networks with rather close meshes. Of course, 

 the varying states of expansion and contraction in the ultimate 

 alveoli, which conditions correspond to phases of activity and 



